For the first time astronomers have combined data from NASA’s Chandra X-ray Observatory and James Webb Space Telescope to study the well-known supernova remnant Cassiopeia A (Cas A), according to the official website of NASA.

As described in our latest press release, this work has helped explain an unusual structure in the debris from the destroyed star called the “Green Monster”, first discovered in Webb data in April 2023. The research has also uncovered new details about the explosion that created Cas A about 340 years ago, from Earth’s perspective.

A new composite image contains X-rays from Chandra (blue), infrared data from Webb (red, green, blue), and optical data from Hubble (red and white). The outer parts of the image also include infrared data from NASA’s Spitzer Space Telescope (red, green and blue). The outline of the Green Monster can be seen in the second image of the carousel.

To learn more about the supernova explosion, the team compared the Webb view of the pristine debris with X-ray maps of radioactive elements that were created in the supernova. They used NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) data to map radioactive titanium — still visible today — and Chandra to map where radioactive nickel was by measuring the locations of iron. Radioactive nickel decays to form iron. An additional image shows the iron-rich debris (tracing where radioactive nickel was located) in green, the radioactive titanium in blue and the pristine debris seen in orange and yellow.

These comparisons suggest that radioactive material seen in X-rays has helped shape the pristine debris near the center of the remnant seen with Webb, forming cavities. The fine structures in the pristine debris were most likely formed when the star’s inner layers were violently mixed with hot, radioactive matter produced during collapse of the star’s core under gravity.

The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

A Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington, NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR’s mission operations center is at the University of California, Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center at the agency’s Goddard Space Flight Center in Greenbelt, Maryland. ASI provides the mission’s ground station and a mirror data archive. Caltech manages JPL for NASA.